Double-strand breaks occur naturally about ten times a day in every human cell; they are one of the most highly toxic and mutagenic kinds of DNA damage, implicated in cancer and many other diseases. Because cancer cells are more susceptible to damage than many normal cells when dividing, DSBs are created deliberately in most cancer therapies to kill dividing tumor cells. But the deliberate inactivation of DNA repair pathways may be an even more powerful method of killing cancer cells, because cancer cells often have defects in repair or signaling of DNA damage which would cripple them if left unrepaired.
Thus the MRN complex, a crucial component of the homologous-recombination method of DSB repair, is a key target for both new cancer therapeutics and for controlled gene targeting to treat inherited disorders in humans as well, plus having numerous other research applications.
What the Tainer team reports in Cell is that Mre11 not only finds the ends of broken DNA strands and links them together but also remodels the DNA in preparation for the work of other repair proteins, an essential function of Mre11 on which successful homologous recombination depends. Additional studies allowed the researchers to determine how mutations of the mre11 gene affect the protein's ability to do its job and in some cases to cause disease.
Prompt and accurate DNA repair is so essential to life that many of the molecular machines that perform DNA repair have changed little throughout the long course of evolution; today these machines show remarkable similarity in organisms as diverse as archaea, yeast, frogs, and human beings.
One consequence is that information about how Mre11 works in humans can be derived from organisms in which proteins a
|Contact: Paul Preuss|
DOE/Lawrence Berkeley National Laboratory